Into the Garden: Identifying weeds is just the beginning

CHARLESTON, W.Va. -- Weeds. Sometimes it's hard to figure out which plants are weeds and which ones are just offspring of something desirable. And then there's the problem of how to get rid of them.

Let's start with the identification.

There are hundreds of websites aimed at weed identification. After visiting 20 or more of these sites, I found that many lead to the same ID tool from the Weed Research & Information Center. I found this one hard to use and frustrating.

The University of Tennessee has a good weed identifier, as does Michigan State's extension service (www.msuturfweeds.com).

The best site, with the best photographs, is run by the University of California Agriculture & Natural Resources Department, www.ipm.ucdavis.edu/PMG/weeds_intro.html. This website, a product of the statewide integrated pest management program, is easy to navigate, and has great photos to help identify all of the weeds in your garden.

The biggest question, after identification, is control. I'm sorry to say there are only a couple of options.

The best option is prevention. A healthy garden and lawn, regularly tended, will keep weeds at bay. Using a pre-emergent weed killer, such as Preen, helps. Pulling weeds before they germinate is critical. But for those of us who have let some of our beds "go to seed," so to speak, the alternatives are usually pulling by hand or using herbicides.

I can't use chemicals in my beds, because the weeds are often closely mixed with the "real" plants. So I'm always pulling, pulling, pulling. I've included chemical control suggestions for those of you who use herbicides.

Here are the ones I'm battling in my yard.

Ground ivy

Ground ivy (Glechoma hederacea), also known as creeping Charlie, is an aggressive, low-growing, perennial invader of lawns, vegetable gardens and flower beds. It thrives in moist, shady areas as well as sunny locations. The scalloped leaves are round or kidney-shaped and are attached by petioles to square stems.

Ground ivy spreads via creeping stems that propagate new plants. Ground ivy will root at each joint whenever it touches the soil, thus making it difficult to pull. Ground ivy spreads by seed and stolons. It can root at each leaf node, so it establishes itself very quickly. Another problem with pulling is the difficulty in getting the whole plant. Rooted nodes left behind will grow and spread.

Ground ivy is hard to control because many commercial broadleaf lawn weed killers have little or no effect on it. Pre-emergence herbicides do not control it; accordingly, we are left with post-emergence controls. Most common broad-leaved weed controls are ineffective by themselves.

The most effective control comes with the use of combination herbicides that contain the product dicamba, applied from mid-September to early November. The next-best time to control ground ivy is when it is just beginning to flower, at the end of April. Two herbicide applications, spaced about 28 days apart are usually needed.

Broadleaf plantain

Broadleaf plantain is common in lawns. It is a cool-season perennial weed found practically in any habitat. The leaves are arranged in a rosette and have prominent veins. Depending on the species, leaves and stems may range from purplish to dark green in color and may be smooth or densely covered with short hairs. Seed heads are rattail-like and 5 to 10 inches long.

Both buckhorn, or narrow-leaved plantain (Plantago lanceolata), and broadleaf plantain (Plantago major) are perennial weeds that reproduce by seeds. Both produce a rosette or cluster of leaves at ground level and have fibrous root systems.

Both plantains produce erect flower stalks from June to September. Seed germinates in late spring through midsummer and sporadically in early fall.

Hand pulling is a simple, practical approach for small areas. Post-emergence herbicides are available depending on the kind of turfgrass in your lawn. Optimum timing of post-emergence herbicides is mid-autumn.

Chickweed

Common chickweed (Stellaria media) is a matted, herbaceous, winter annual broadleaf plant. It thrives under cool, wet conditions and is a prolific spring weed. It rarely tolerates the hot, dry conditions of late spring or early summer. Other common names for chickweed are starweed, bindweed, winterweed, satin flower and tongue grass.

Although chickweed is commonly referred to as a weed, it does have a place in folk medicine as a remedy for asthma, constipation, cough, fever and various other ailments. The seed of chickweed is a source of food for birds.

Common chickweed develops prostrate, tender, freely branching stems that root at nodes; opposite, smooth, oval leaves; shallow, fibrous and very frail roots; flowers are solitary or in small clusters at ends of stems. Plants form a thick mat of succulent or tender vegetation in the early spring that is not eradicated by close mowing.

The stems creep along the ground and can root at the nodes. Common chickweed is effectively controlled by timely applications of pre-emergent herbicides made in early fall before the emergence of chickweed.

Post-emergent control of chickweed in early spring can be achieved with products containing dicamba, dichlorprop and triclopyr. The latter product is only labeled for use on cool season turfgrasses such as tall fescue, bluegrass and perennial ryegrass.

Carolina geranium

Carolina geranium is often confused with ground ivy, but the leaves are deeply dissected into five to seven lobes, each of which is again lobed and bluntly toothed on the margins.

The plant produces a deep taproot. Flowers have five pink to lavender petals. Seeds have a conspicuous cranesbill beak about a half-inch long.

Hand pulling is easy and effective. Maintain a dense, healthy lawn that crowds out weeds naturally and reduces the chances for invasion. Apply mulch to ornamental beds.

Thistle

There are many thistles that plague our area. I've tried to identify the one in my bed, and I think I have Canada thistle. Unlike other thistles, the male and female flowers appear on separate plants in the Canada thistle. (Male and female parts may appear together, but only one sex is fertile.)

Honeybees are the main pollinators of Canada thistle. Individual plants produce an average of 1,500 seeds, but there must be both male and female plants in the vicinity for successful pollination. About 90 percent of the seeds will germinate within one year, but other seeds can remain viable for about 20 years. Seeds can be blown a half-mile in the wind.

The seedlings require full sun for normal development. Growth is reduced if full sunlight is not available, and the seedlings die when shade reduces light intensity to 20 percent.

Canada thistle has a deep and wide-spreading root system. Hand-pulling or cutting Canada thistle can stimulate the plants to send up more sprouts from the roots; however, repetitive treatments might starve underground stems. Cultivating chops the roots into little pieces that sprout new thistles; cultivating is only successful if it is repeated every 10 to 15 days through the growing season for up to two years.

Mugwort

This aromatic perennial with a branching rootstock is native along highways and ditches. It is tolerant of a wide range of soil types and pH. It is able to survive in both cool, dry, and in warm, wet conditions, but not in shaded and grazed sites.

Mugwort can grow up to 4 feet tall and forms dense stands that smother other vegetation. In the vegetative state, it has the appearance of a garden chrysanthemum, hence some of the common names. Mugwort is widely used in herbal medicine including use as a diuretic and the treatment of a variety of gynecological problems.

Mugwort seeds have remained viable in cultivated soil for at least five years. Seed recovered during house demolitions and dated at 30 or more years is reported to have germinated. The weed is commonly dispersed by floodwater.

Mugwort spreads slowly by short rhizomes. It can propagate from small rhizome fragments. The rhizomes may be spread or transported by cultivation equipment and among the roots of transplanted herbaceous plants infested with the weed. Rhizome fragments can also be transported in topsoil.